Automatic pilot control equipment



June 5, 1962 H. w. PATTON 3,

AUTOMATIC PILOT CONTROL EQUIPMENT Original Filed Sept. 15, 1956 3heets-Sheet 1 HF ,O EF 'EF Fizz; 1

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OUTPUT [0y Pan 1? 64m 2500 5V 4 I I CONTROL CURRENT I60 500 Q 2VINVENTOR. HEN/P) Ml R4rro/v A r ra a/var June 5, 1962 H. w. PATTONAUTOMATIC PILOT CONTROL EQUIPMENT 3 Sheets-Sheet 2 Original Filed Sept.15, 1956 M MwNN Q NQEEE wvib w koilokbq INVENTOR. HENRY W PA TTON 8ATTORNEY June 5, 1962 H. w. PATTON AUTOMATIC PILOT CONTROL EQUIPMENTOriginal Filed Sept. 13. 1956 3 Sheets-Sheet 3 INVENTOR. HL'NRY W PATTON5 y United States Patent 3,038,114 AUTOMATIC PILOT CONTROL EQUIPMENTHenry W. Patton, Cedar Rapids, Iowa, assignor to C01- lins RadioCompany, Cedar Rapids, Iowa, a corporation of Iowa Original applicationSept. 13, 1956, Ser. No. 609,720. Divided and this application Apr. 22,1959, Ser. No.

3 Claims. (Cl. 32389) This invention relates to automatic pilot flightcontrol equipment and more specifically to such equipment for changingflight control functions without generating disturbing transienteffects. The present invention relates to a clamping control circuit foran amplifier, subject matter of which is divided from my copendingapplication Serial No. 609,720, filed September 13, 1956.

In automatic flight control equipment, it is often desired to switchfrom one flying function to another, such as from glide slope to gyroand to hold altitude flight functions. The switching of the control ofthe aircraft from one of these flight functions to another must be donesmoothly or, as it is sometimes said, one function must be faded intoanother. This fading is required to prevent undesired violent maneuversof the aircraft during the changing of flight functions. This inventionprovides an amplifier circuit which is controlled by a clamp circuit tolimit the amplification of the amplifier. The system is controlled by adirect current potential applied to saturable reactors in conjunctionwith alternating current supply signals. The alternating current outputof the saturable reactors is applied to a rectifier circuit, the outputof which is filtered and applied to the amplifier to control its gain.Thus, the direct current applied to the saturable reactor controls theflight functions by causing the total gain of the signal amplifier tovary.

It is a feature of this invention that automatic flight controlequipment is controlled both as to its gain and as to the rapidity ofits total energization or gain by the application of a direct currentvoltage. It is a further feature of this invention that automatic flightcontrol equipment may be smoothly switched from One flight function toanother without generating disturbing transient effects to disruptflight of the aircraft.

It is an object of this invention to provide a control system forautomatic flight control systems which will enable the pilot to engagethe automatic pilot system and to change the flight functions of thesystem without generating disturbing transients to noticeably affect theflight of the aircraft. It is another object of this invention toprovide a control system for an automatic flight control system which iseconomical to construct, simple, and essentially fail-proof. It is astill further object of this invention to provide a control system forautomatic pilot systems where one switch controls several operatingchannels, such as aileron, rudder, etc. It is still another object toprovide a control system which will enable the pilot to switch operatingfunctions from one to another easily and simply with no separate controlnecessary to minimize the transient effects of the change.

These and other objects of this invention will become apparent when thefollowing description is read in conjunction with the accompanyingdrawings, in which:

FIGURE 1 is a diagram of one embodiment of an amplifier circuit of thisinvention;

3,038,114 Patented June 5, 1962 FIGURE 2 is a graphical representationof the gain characteristics of the amplifier of FIGURE 1 with variousclamp voltages applied;

FIGURE 3 is a schematic representation of this invention applied to asingle autopilot signal channel; and

FIGURE 4 is a schematic representation of this invention applied to aplurality of signal channels for flight functions. 7

Referring now to FIGURE 1, this amplifier circuit has accurate gaincontrol characteristics which are controlled by the impedance acrossterminals 5 and 10. This amplifier is well known in the art and controlsits gain by negative feedback means. The amplifier utilizes corematerials having an essentially rectangular hysteresis characteristic.The addition of the diodes 6 and 7 and the resistors 8 and 9 to thewell-known negative feedback amplifier provides novel clamp means tocontrol the gain of the amplifier circuit. With no direct currentvoltage applied to the clamp circuit, diodes 6 and 7 effectively providea short-circuit across terminals 10 and 5, which results insubstantially zero gain by the amplifier. The amount of gain of theamplifier is changed immediately upon the application of a directcurrent voltage of the clamp circuit. A direct current voltage appliedto the clamp circuit of either polarity unblocks the diodes 6 and 7 sothat full gain is exhibited by the amplifier circuit. Full gain ismaintained in the amplifier circuit until the output signal potentialacross the output resistors reaches one-half of the applied directcurrent clamp voltage. At this point, the potential applied to thediodes 6 and 7 in the clamp circuit will reverse polarity and thisreduces the gain of the magnetic amplifier to zero once more. The gaincontrol characteristics of the amplifier circuit of FIGURE 1 withvarious values of clamp voltage, namely 2, 5, and 10 volts, are shown inFIGURE 2. It is obvious from FIGURE 2 that the operating characteristicsand the maximum gain characteristics may be accurately controlled bycontrolling the amount of direct current clamp voltage applied to theamplifier of this invention.

Referring now to FIGURE 3, which depicts a novel circuit for generatingthe direct current voltage for application to the amplifier of FIGURE 1,terminals 27 and 7.8 are connected through a switch 41 to a directcurrent source which is applied through a delay network 29 to asaturating reactor 31. The AC. windings of the saturating reactor 31 areconnected to an alternating current source 30 which aboard aircraftnormally has a frequency of 400 cycles per second. The saturationcharacteristics of the saturating reactor 31 are thus directlycontrolled by the direct current applied to the windings of the reactor.The output circuit of the saturating reactor is connected to a diodebridge 32. The other side of the bridge is connected to the filternetwork 33 for filtering before application to the terminals 12 and 13which may be connected to like terminals 12 and 13 of the clamp circuitof FIG- URE l. The controlled preamplifier of FIGURE 3 may be anamplifier such as that shown in FIGURE 1. The information input signalto the controlled preamplifier is a control signal for operating therudder, ailerons, etc. of the aircraft, and the output signal from thecontrolled preamplifier is applied directly or after mixing with otherinformation signals to a power amplifier; thence to a control surface.

Referring now to FIGURE 4, a plurality of circuits similar to that ofFIGURE 3 are arranged so that one function switch on the aircraft cancontrol the flight of the aircraft so as to fly in any one of aplurality of functions. The switching of the function switch 41 tocontacts 51, 52, or 53 obviously will apply a direct current signalthrough diodes 42, 43, 44, or 45 to a plurality of filter delay networks29 and then to a plurality of saturable reactors 31 in exactly the samefashion as that described for FIGURE 3. The outputs of the rectifierbridges 32 in FIGURE 4 are then applied to clamps 1, 2, 3, or 4, whichare connected to predetermined preamplifiers by appropriate filters soas to control the flight of the aircraft in the function directed by theswitch 41. With the switch 41 in the position shown in FIGURE 4, currentwill pass through diodes 42 and 44 to the respective saturable reactors31. The outputs of the saturable reactors 31 are supplied through thedelay network 29. The saturable reactors will generate an output currentwhich will be applied to the respective rectifier bridge circuits 32 andthe respective filter networks 33 and so a signal is applied to theclamp of amplifier 2 and amplifier 4. Thus the amplifiers 2 and 4 connected to clamps 2 and 4 will have a voltage applied and theseamplifiers will be permitted to amplify. This amplification results asdescribed for FIGURE 1 by the unblocking of the amplifiers byapplication of the direct current voltage. These amplifiers then willamplify to a given value dependent upon the gain characteristics of theamplifier and the amount of direct current voltage applied, this directcurrent voltage being controllable by the amount of direct currentapplied to the saturating reactor. It is particularly important to notethat only one switch, 41, is required for all the switching functions inthis automatic pilot system. This invention also eliminates many relaysand contacts required in prior inventions. This invention alsoprovides-for fading time to be automatically inserted by the delayfilters 29 so that any generated transient effects are smoothed out.Thus this invention switches flight controlfrom one flight function to anew flight function smoothly. The various amplifiers required for thisinvention are connected as shown in FIGURE 4 for integration purposesand it is to be remembered that each output from the filters 33 inFIGURE 4 is applied to the clamp circuit of a particular preamplifier asshown in FIGURES 1 and 3. Thus, this invention provides a method forsmoothly switching flight functions, but no attemptis made herein todescribe the automatic pilot system required, or the completeintegration of the signals from gyro and glide slope, etc. Thisintegration is accomplished in other circuitry in most automatic pilotsystems and it is not necessary that it be described to explain theoperation of this invention.

Although this invention has been described with respect to a particularembodiment thereof, it is not to be so limited, as changes andmodifications may be made therein which are within-the full intendedscope of the invention, as defined by the appended claims.

What is claimed is:

1. 'In a magnetic amplifier of the type including a plurality ofsatur-able core members each having associated therewith an input signalcontrol winding, a power winding, and a feedback winding, and a gaincontrolling resistive network serially and symmetrically connected withsaid feedback windings and the output terminals of said amplifier; meansfor controlling the gain of said amplifier, said means including saidresistive network and ftuther comprising first and second unilateralconduction devices serially connected in opposite polarization withfirst and second resistive members respectively, each said seriallyconnected unilateral device and resistive member connected across theterminals of said gain controlling resistive network, a source ofdirect-current voltage connected between the junctions of each of saidunilateral conduction devices and the associated one of said first andsecond resistors, said direct-current source being polarized with thepositive and negative terminals thereof 4 connected to the cathode andanode electrodes respectively of said unilateral conduction devices,whereby said amplifier is rendered conductive by and the output of saidamplifier is limited at a predetermined magnitude in accordance with thepresence of and the magnitude respec tively of said source of directcurrent.

2. An amplifier gain control circuit comprising switch ing means, asource of direct current voltage, a delay network connectable to saidsource of direct current voltage through said switching means, asaturable reactor including a control winding and an output winding,said control winding connected to the output of said delay network, asource of alternating current voltage, full wave rectifying meansincluding an input and an output, the output winding of said saturablereactor serially connected with said alternating current voltage sourceand the input to said rectifying means, a filter network connected tothe output of said rectifying means, an input information signal source,a magnetic amplifier including a plurality of saturable core memberseach having associated therewith an input signal control winding towhich said input information signal source is connected, a powerwinding, and a feedback winding, and a gain controlling resistivenetwork serially and symmetrically connected with said feedback windingsand the output terminals of said amplifier, direct-current voltageresponsive-gain-control means includ ing said resistive network andfurther comprising first and second unilateral conduction devicesserially connected in opposite polarization with first and secondresistive members respectively, each said serially connected unilateraldevice and resistive member connected across the terminals of said gaincontrolling resistive network; the output of said filter networkconnected between the junctions of each of said unilateral conductiondevices and the associated one of said first and second resistors, saidfilter network output being polarized with the positive and negativeterminals thereof connected to the cathode and anode electrodesrespectively of said first and second unilateral conduction devices,whereby said amplifier is selectively rendered conductive by, and theoutput of said amplifier is limited at, a predetermined magnitude inaccordance with the presence of and the magnitude respectively of theoutput of said filter network.

3. An amplifier gain control circuit comprising a selection switch, asource of direct current voltage, a delay network connectable to saidsource of direct current voltage through said selection switch, asaturable reactor having a control winding and an output winding withsaid control winding connected to said delay network, a source ofalternating current voltage, one side of said alternating voltage sourceconnected to one end of the output winding of said saturable reactor, adiode bridge rectifier circuit including pairs of input and outputterminals, one input terminal of said diode bridge circuit connected tothe other end of the output winding of the saturable reactor, the otherinput terminal of said diode bridge rectifier connected to the otherside of the alternating current voltage source, a filter networkconnected to the output terminals of the diode bridge rectifier, asource of information signals; a magnetic amplifier including aplurality of saturable core members each having associated therewith aninput signal control winding to which said source of information signalsis connected, a power winding, and a feedback winding, and a gaincontrolling resistive network serially and symmetrically connected withsaid feedback windings and the output terminals of said amplifier,directcurrent voltage responsive-gain-control means including saidresistive network and further comprising first and second unilateralconduction devices serially connected in opposite polarization withfirst and second resistive members respectively, each said seriallyconnected unilateral device and resistive member connected across theterminals of said gain controlling resistive network, said selectionswitch selectively connecting said source of direct current voltage tosaid delay means thereby effecting a predetermined saturation in saidreactor, said diode bridge circuit being adapted to produce a directcurrent output signal with magnitude proportional to the degree ofsaturation of said reactor, the output of said filter network connectedbetween the junctions of each of said unilateral conduction devices andthe associated one of said first and second resistors, said filternetwork output being polarized with the positive and negative terminalsthereof connected to the cathode and anode electrodes respectively ofsaid first and second unilateral conduction devices, whereby saidamplifier is rendered conductive by and the output 6 of said amplifieris limited at a predetermined magnitude in accordance with the presenceof and the magnitude respectively of said filter network output.

References Cited in the file of this patent UNITED STATES PATENTS2,473,617 Stiefel June 21, 1945 2,518,865 Cartotto Apr. 15, 19502,681,268 Ramson et al Mar. 10, 1953 10 2,700,130 Geyger Jan. 18, 1955

